Rectangular block transform scaling

Abstract

A device for decoding video data determines a quantization parameter (QP) for a block of transform coefficients, wherein the block of transform coefficients is a non-square, rectangular block; determines a value for (log2 (width)+log2 (height), wherein width represents a width of the block of transform coefficients and height represents a height of the block of transform coefficients; in response to the value not being divisible by 2, determines a modified QP for the block of transform coefficients based on the QP; inverse transforms the transform coefficients to determine a block of quantized residual samples; and dequantizes the quantized residual samples based on the modified QP to determine a block of residual samples.

What is claimed is: 
     
       1. A method of decoding video data, the method comprising:
 determining a first quantization parameter (QP) for a block of first transform coefficients, wherein the block of the first transform coefficients is a non-square, rectangular block; 
 determining that a value for (log 2  (width)+log 2  (height)) is not divisible by 2, wherein width represents a width of the block of the first transform coefficients and height represents a height of the block of the first transform coefficients; 
 in response to the value not being divisible by 2, mapping the first QP to QP-3 to determine a modified QP; 
 inverse transforming the first transform coefficients to determine a block of first quantized residual samples; 
 dequantizing the first quantized residual samples based on the modified QP to determine a block of first residual samples; 
 determining a second QP for a block of second transform coefficients, wherein the block of the second transform coefficients is a second non-square block; 
 inverse transforming the second transform coefficients to determine a block of second quantized residual samples; 
 determining that a second value for (log 2  (width 2)+log 2  (height2)) is divisible by 2, wherein width2 represents a width of the block of the second transform coefficients and height2 represents a height of the block of the second transform coefficients; and 
 in response to the second value being divisible by 2, dequantizing the second quantized residual samples based on the second QP to determine a block of second residual samples. 
 
     
     
       2. The method of  claim 1 , further comprising:
 determining a scaling parameter based on the modified QP; and 
 dequantizing the first quantized residual samples based on the scaling factor to determine the block of the first residual samples. 
 
     
     
       3. The method of  claim 1 , further comprising:
 determining a shifting parameter based on the modified QP; and 
 dequantizing the first quantized residual samples based on the shifting parameter to determine the block of the first residual samples. 
 
     
     
       4. The method of  claim 1 , further comprising:
 adding the block of the first residual samples to a prediction block to determine a reconstructed block. 
 
     
     
       5. The method of  claim 4 , further comprising:
 performing one or more filtering operations on the reconstructed block to determine a decoded block of video data; and 
 outputting a decoded picture comprising the decoded block of the video data. 
 
     
     
       6. The method of  claim 5 , wherein outputting the decoded picture comprises storing decoded picture in a decoded picture buffer, the method further comprising:
 encoding one or more additional pictures based on the decoded picture. 
 
     
     
       7. The method of  claim 5 , wherein outputting the decoded picture comprises displaying the decoded picture. 
     
     
       8. A device for decoding video data, the device comprising:
 a memory configured to store video data; and 
 one or more processors implemented in circuitry and configured to:
 determine a first quantization parameter (QP) for a block of first transform coefficients, wherein the block of the first transform coefficients is a non-square, rectangular block; 
 determine that a value for (log 2  (width)+log 2  (height)) is not divisible by 2, wherein width represents a width of the block of the first transform coefficients and height represents a height of the block of the first transform coefficients; 
 in response to the value not being divisible by 2, map the first QP to QP-3 to determine a modified QP; 
 inverse transform the first transform coefficients to determine a block of first quantized residual samples; 
 dequantize the first quantized residual samples based on the modified QP to determine a block of first residual samples; 
 determine a second QP for a block of second transform coefficients, wherein the block of the second transform coefficients is a second non-square block; 
 inverse transform the second transform coefficients to determine a block of second quantized residual samples; 
 determine that a second value for (log 2  (width 2)+log 2  (height2)) is divisible by 2, wherein width2 represents a width of the block of the second transform coefficients and height2 represents a height of the block of the second transform coefficients; and 
 in response to the second value being divisible by 2, dequantize the second quantized residual samples based on the second QP to determine a block of second residual samples. 
 
 
     
     
       9. The device of  claim 8 , wherein the one or more processors are further configured to:
 determine a scaling parameter based on the modified QP; and 
 dequantize the first quantized residual samples based on the scaling factor to determine the block of the first residual samples. 
 
     
     
       10. The device of  claim 8 , wherein the one or more processors are further configured to:
 determine a shifting parameter based on the modified QP; and 
 dequantize the first quantized residual samples based on the shifting parameter to determine the block of the first residual samples. 
 
     
     
       11. The device of  claim 8 , wherein the one or more processors are further configured to:
 add the block of the first residual samples to a prediction block to determine a reconstructed block. 
 
     
     
       12. The device of  claim 11 , wherein the one or more processors are further configured to:
 perform one or more filtering operations on the reconstructed block to determine a decoded block of video data; and 
 output a decoded picture comprising the decoded block of the video data. 
 
     
     
       13. The device of  claim 12 , wherein to output the decoded picture, the one or more processors are further configured to store the decoded picture in a decoded picture buffer, wherein the one or more processors are further configured to:
 encode one or more additional pictures based on the decoded picture. 
 
     
     
       14. The device of  claim 12 , further comprising:
 a display configured to display decoded video data; 
 wherein to output the decoded picture, the one or more processors are further configured to display the decoded picture on the display. 
 
     
     
       15. The device of  claim 8 , wherein the device comprises one or more of a camera, a computer, a mobile device, a broadcast receiver device, or a set-top box. 
     
     
       16. A computer-readable storage medium storing instructions that when executed by one or more processors cause the one or more processors to:
 determine a first quantization parameter (QP) for a block of first transform coefficients, wherein the block of the first transform coefficients is a non-square, rectangular block; 
 determine that a value for (log 2  (width)+log 2  (height)) is not divisible by 2, wherein width represents a width of the block of the first transform coefficients and height represents a height of the block of the first transform coefficients; 
 in response to the value not being divisible by 2, map the first QP to QP-3 to determine a modified QP; 
 inverse transform the first transform coefficients to determine a block of first quantized residual samples; 
 dequantize the first quantized residual samples based on the modified QP to determine a block of first residual samples; 
 determine a second QP for a block of second transform coefficients, wherein the block of the second transform coefficients is a second non-square block; 
 inverse transform the second transform coefficients to determine a block of second quantized residual samples; 
 determine that a second value for (log 2  (width 2)+log 2  (height2)) is divisible by 2, wherein width2 represents a width of the block of the second transform coefficients and height2 represents a height of the block of the second transform coefficients; and 
 in response to the second value being divisible by 2, dequantize the second quantized residual samples based on the second QP to determine a block of second residual samples. 
 
     
     
       17. The computer-readable storage medium of  claim 16 , storing further instructions that when executed by the one or more processors cause the one or more processors to:
 determine a scaling parameter based on the modified QP; and 
 dequantize the first quantized residual samples based on the scaling factor to determine the block of the first residual samples. 
 
     
     
       18. The computer-readable storage medium of  claim 16 , storing further instructions that when executed by the one or more processors cause the one or more processors to:
 determine a shifting parameter based on the modified QP; and 
 dequantize the first quantized residual samples based on the shifting parameter to determine the block of the first residual samples. 
 
     
     
       19. The computer-readable storage medium of  claim 16 , storing further instructions that when executed by the one or more processors cause the one or more processors to:
 add the block of the first residual samples to a prediction block to determine a reconstructed block; 
 perform one or more filtering operations on the reconstructed block to determine a decoded block of video data; and 
 output a decoded picture comprising the decoded block of the video data, wherein outputting the decoded picture comprises displaying the decoded picture. 
 
     
     
       20. An apparatus for decoding video data, the apparatus comprising:
 means for determining a first quantization parameter (QP) for a block of first transform coefficients, wherein the block of the first transform coefficients is a non-square, rectangular block; 
 means for determining that a value for (log 2  (width)+log 2  (height)) is not divisible by 2, wherein width represents a width of the block of the first transform coefficients and height represents a height of the block of the first transform coefficients; 
 means for mapping the first QP to QP-3 to determine a modified QP in response to the value not being divisible by 2; 
 means for inverse transforming the first transform coefficients to determine a block of first quantized residual samples; 
 means for dequantizing the first quantized residual samples based on the modified QP to determine a block of first residual samples; 
 means for determining a second QP for a block of second transform coefficients, wherein the block of the second transform coefficients is a second non-square block; 
 means for inverse transforming the second transform coefficients to determine a block of second quantized residual samples; 
 means for determining that a second value for (log 2  (width 2)+log 2  (height2)) is divisible by 2, wherein width2 represents a width of the block of the second transform coefficients and height2 represents a height of the block of the second transform coefficients; and 
 means for dequantizing the second quantized residual samples based on the second QP to determine a block of second residual samples in response to the second value being divisible by 2. 
 
     
     
       21. The apparatus of  claim 20 , further comprising:
 means for determining a scaling parameter based on the modified QP; and 
 means for dequantizing the first quantized residual samples based on the scaling factor to determine the block of the first residual samples. 
 
     
     
       22. The apparatus of  claim 20 , further comprising:
 means for determining a shifting parameter based on the modified QP; and 
 means for dequantizing the first quantized residual samples based on the shifting parameter to determine the block of the first residual samples.